One of the concerns North Korea experts have about Trump is that his faith in his instincts masks a shallow understanding of the intricacies of nuclear diplomacy. Kim, who is showing increasing strategic sophistication on the other hand, is likely to be sharply focused on the details since his nuclear arsenal is seen in Pyongyang as the guarantor of his dynastic rule.

Trump said on Saturday he would know within seconds of the start of their talks in Singapore on Tuesday if the whole thing is going to work out.

"The first minute I'll know -- just my touch, my feel, that's what I do," Trump told reporters at the G7 summit in Canada.

Earlier in the week, Trump said he didn't have to prepare very much for the meeting because it was all about "attitude." Then on Friday, the former real estate tycoon insisted he had actually been preparing for his encounter with Kim "all my life."

Whether Trump is truly winging it or he just wants everyone to think so after days of quiet preparations is unclear.

But the danger of going into the summit undercooked is that Trump could make inadvertent concessions on complicated or historically fraught issues, or adopt positions that are detrimental to allies like South Korea or Japan, or stumble into North Korean negotiating traps.

If the summit goes well, it is likely to lead to the kind of long-term diplomatic engagement with the North Koreans that is familiar from past presidencies that the current administration said it would not permit. It will require intense US focus, endurance and attention to detail to achieve an accounting of Pyongyang's nuclear arsenal and its verifiable and irreversible termination.

Kim will do his homework

Despite their isolation and the image of North Korea as a backward state, North Korean negotiators are always well-briefed, and a new generation of younger diplomats is savvier about the outside world than their older counterparts.

"We shouldn't be fooled by our notion that North Korea is a hermit kingdom," said Wendy Sherman, a former senior State Department official who negotiated with North Korea on an ultimately unsuccessful missile deal at the end of the Clinton administration.

"We saw Kim Jong Un very ably manage the summit with (South Korean President) Moon Jae-In. He is prepared, he will do his homework."

Still, Trump does have one major advantage over US officials who took part in failed previous negotiations with North Korea -- he's getting to meet the man who is in charge.

Evans Revere served as one of the State Department's top Asia experts and was often frustrated that his counterparts were unable to make the most crucial decisions.

"So often we were dealing with people who were posturing, reading talking points, who were engaged in bluster, but at the end of the day, weren't really the people who could resolve the issues we were trying to resolve. There was a lot of gamesmanship," Revere said.

"One of the benefits of what we are doing right now is we are actually talking to the inner circle of the leadership who have the ability to resolve the issues and have the ability to take action."

In recent days, Trump has admitted that the summit is only the start of an effort to denuclearize the Korean peninsula and end a state of war between Pyongyang and the US, rolling back more ambitious earlier administration predictions of a much faster process.

That means it could lead to a period of intense and exhausting negotiations with the North Koreans familiar from the Clinton, Bush and Obama administrations.

Former senior US diplomat Christopher Hill, who led negotiations with Pyongyang during the Bush years, described just how frustrating the process could get in his autobiography "Outpost."

"Whether it is in their manual of negotiation or not, the North Koreans would have an annoying habit of agreeing to something, then coming back and not agreeing to what they had just agreed," Hill wrote.

Revere, now with the Albright Stonebridge Group, a global strategic advisory firm, said that despite the North's isolation and the paranoia it sometimes causes, North Korean negotiating teams are sophisticated, even if there are questions about whether they fully grasp all the intricacies of nuclear strategy.

"They have done their homework, they are very skilled," he said. "They are obviously all very loyal to the cause and loyal to the leadership, (but) they are extremely skilled at what they do."

Intelligence on Kim

Trump has the advantage heading into the talks of the experience gleaned about Kim's approach by Secretary of State Mike Pompeo who has met the North Korean leader several times, as well as information passed on by Moon.

While Kim is often lampooned over his hairstyle, his style of dress and the rudimentary state of North Korea's civilian air fleet, he has demonstrated an impressive ability to consolidate power and to conduct an aggressive and strategic foreign policy since becoming supreme leader in 2011.

His race to expand his nuclear arsenal and long-range missiles to deliver it may now have been replaced by a strategic choice to use that leverage to alleviate the severe economic situation in his country and its diplomatic isolation.

He has managed to win the ultimate prize of a summit with an American President -- a step neither of his two dynastic predecessors managed without offering any major concessions.

Kim, who was educated in Switzerland, is likely to have a panoramic sense of his objectives, North Korea's nuclear program and the strategic picture in Northeast Asia experts said.

Diplomats who met his late father, Kim Jong Il, remember his understanding of the key issues, a trait his son appears to share.

"Kim Jong Il went down that entire list ... and although he didn't have every detailed answer to everything, he knew what the questions were, what the issues were, he was well-prepared," she said.

Both Kim and Trump have a strong incentive to declare the summit a success whatever happens. Trump's approach is to try and forge a personal connection with Kim, in line with his belief that relationships are the key to dealmaking in international relations.

Critics have faulted the President for an overly conciliatory approach to the North Korean leader, who presides over the world's most oppressive state, where millions of people have died of hunger and which maintains a network of gulags and reeducation camps.

"It's unknown territory, in the truest sense," Trump told reporters.

"I feel that Kim Jong Un wants to do something great for his people, and he has that opportunity, and he won't have that opportunity again," Trump said. "So, I really believe that he's going to do something very positive."

In his speeches and actions, Kim has shown that he has a sense of his own position in history, though he has yet to publicly give any sign that he is willing to follow through on denuclearization.

But Trump's gambit appears to be aimed at convincing Kim that more personal respect and recognition could follow if he commits to a serious negotiating process with Washington.

If it works, Trump could be in reach of an achievement that has eluded all his predecessors and could define his foreign policy legacy.